What is the difference between US stock and Euro stock?
Slightly different beam pattern with more light higher on the right side.
What are E-Code headlights?
Euro stock - different beam pattern. They usually throw more more light higher on the right side.
What are Projector headlights?
The main advantage of projector headlights is to provide a controlled beam with an even light dispersal throughout the width of the beam.
Projectors also allow manufacturers to make more compact headlights for styling purposes.
There are 3 main types of projectors:
1.
Halogen projectors - designed for halogen bulbs, as the name implies.
3.
HID (xenon) Projectors - designed for HID bulbs
3.
HID Bi-Xenon Projectors - have a built in high beam function
There's a night and day difference between Halogen and HID projectors. The geometry of the 2 is entirely different. If you put an HID into a halogen projector, chances are there won't be much improvement and you risk blinding oncoming traffic.
Halogen Projector from a New Beetle
HID headlights are those specifically designed for HIDs (only). The best are based on an HID specific projector. Many are retrofitting their headlights with aftermarket HID projectors, such as the FX-R bi-xenon or Mini bi-xenon.
HIDs don't use a filament to generate light. An HID bulb contains an arc chamber (capsule) that creates light via plasma. As the name implies, the arc chamber is filled with Xenon gas and metal halid salts. On startup, approx. 25,000 volts is passed through the arc chamber, vaporizing the metal halid salts and generating plasma. Once the plasma is established, the voltage ramps down to approx 85v AC. The voltages are supplied by a ballast, which is contained in a small, usually metal box.
An HID "bulb" typically outputs 3x the light of a halogen bulb. HIDs can be made in varying colors, but the best and brightest HIDs range from 4100K to 5000K color temperature. (yellowish-white to bright white). The blue and purple hids are higher color temperatures. The higher the color temperature, the lower the light output of HIDs.
Here's a couple of shots I swiped of the internet to give you an idea:
Halogen on left, HID in halogen projector on right
HID in a true HID Projector
If you want more information, a good source is:
www.HIDPlanet.com
Spend some time reading there and you can learn all you ever wanted to know about HIDs and retrofitting.